Which machine learning approach did Spotify first use to power its famous music recommendation system?

Streaming platforms have transformed how we discover and consume music, but few people know about the sophisticated machine learning algorithms powering these recommendations. Test your knowledge about how AI and data science have revolutionized the music industry's ability to match listeners with new artists and songs they'll love.

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Collaborative filtering through matrix factorization
Neural networks analyzing audio waveforms
Natural language processing of user reviews
Reinforcement learning based on skip behaviors